Fact Sheets - Calibrating Your Thermometer

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Calibrating Your Thermometer

Thermometers must be maintained to an accuracy of at least plus or minus (±) 1°C. An external contractor, manufacturer or distributor will be able to calibrate the thermometer at least once a year. You can also calibrate thermometers using the following methods.

1. Ice Water Slurry Method

Crush several pieces of ice (about 50-100g) and place in a small container such as a drinking glass.

Add enough cold water to produce a slurry but not so much that the ice floats.

Stir the ice slurry vigorously and let stand for approx 5 minutes.

Insert the thermometer into the slurry and wait at least one to two minutes for the reading to stabilise.

Record the temperature.

Take three further readings at least one minute apart.

If consecutive readings are not within 0.5°C replace or service the thermometer.

If the temperature readings are higher than +1°C or lower than -1°C attach a label to the thermometer showing the date the calibration check was made and the variation from 0°C. Alternatively purchase a new thermometer.

2. Boiling Water method

Bring a container of water to the boil.

Insert the thermometer probe into the boiling water and wait for the reading to stabilise.

Record the temperature.

Take 3 further readings at least 1 minute apart.

The reading should be 100°C.

If the temperature reads higher than 101°C or lower then 99°C attach a label to the thermometer showing the date the calibration check was made and the variation from 100°C. Alternatively purchase a new thermometer.